The present invention relates to glass cutting or scoring machines, and in particular to the mechanism for holding the glass scoring wheel against the sheet to be cut. (The terms "score" and "cut" and their variants are used synonymously herein.) In actual practice, the glass is scored by a scoring wheel and then deformed (usually manually) for severing or breaking the glass sheet along the score lines.
Glass scoring machines of the type under consideration are provided with a table to support the sheet of glass to be cut. The table may be of the tiltable type shown in U.S. Pat. No. 3,570,733 to facilitate handling of the glass sheets which are usually of rather large size and are consequently rather heavy.
The scoring wheel is supported by a pillar post which is in turn supported over the table by a movable carriage. The carriage is numerically controlled and computer operated for movement along X and Y axes to score the glass along straight and curved paths. Representative prior art showing such machines are U.S. Pat. Nos. 4,171,657 and 4,709,483.
During operation of these scoring machines, the carriage remains in fixed vertical relationship with the table. Glass scoring machines of the type under consideration are normally provided with some form of a resilient or yieldable means for establishing the desired force between the scoring wheel and the surface of the glass sheet to be scored. Usually, either a spring or pneumatic system is employed to yieldably urge the scoring wheel against the glass surface. A prior art reference showing the pneumatic type of hold-down mechanism for a scoring wheel is U.S. Pat. No. 3,058,220.
As is known to those skilled in the art, the surface of the table used to support the glass sheet is not perfectly flat or planar. Normally, variations in the surface of the table will be in the range of plus or minus 1/8 of an inch. The glass sheet (which itself is very flat and has a very uniform thickness) will tend to follow or adopt the surface contour of the table both because of the weight of the glass sheet and because of the force applied to the glass sheet by the scoring wheel. Thus, the distance between the carriage and the glass surface to be scored will vary as much as 1/4 of an inch during a scoring operation. By way of reference, the depth of the score is usually about 1/1000 of an inch. Thus, to maintain consistency and uniformity in the depth of the score line, it is necessary to provide means for maintaining the desired force between the scoring wheel and the glass as the scoring wheel moves relative to the carriage to accommodate the undulating surface of the glass sheet.